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arXiv 1003.4512astro-ph.EP
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HAT-P-13系外行星系统:自旋-轨道对准的证据和第三个伴星

The HAT-P-13 Exoplanetary System: Evidence for Spin-Orbit Alignment and a Third Companion

Joshua N. Winn, John Asher Johnson, Andrew W. Howard, Geoffrey W. Marcy, Gaspar A. Bakos, Joel Hartman, Guillermo Torres, Simon Albrecht, Norio Narita

摘要:

我们提出了新的径向速度测量的HAT-P-13,一颗恒星与两个以前已知的同伴:一个过境巨行星“b”的轨道周期为3天,和一个更大的对象“c”的1.2年,高偏心轨道。对于这个系统,动力学的考虑将导致对行星b内部结构的限制,如果它可以证明轨道是共面的,并且是径向锁定的。通过模拟罗西特-麦克劳克林效应,我们发现行星b的轨道角动量矢量和恒星自旋矢量在天空中是对齐的(λ = -0.9 +/- 8.5度),这表明行星轨道也是对齐的。精确的轨道解倾向于行星b的稍微偏心的轨道(e = 0.0142 - 0.0044 ^{+0.0052}),尽管不清楚它是否与c的轨道(Δω= 48 - 38 ^{+25} deg)近距离锁定。我们发现了恒星径向速度的长期趋势,并将其解释为另一个天体“d”的证据,这可能是另一颗行星或低质量恒星。下一次c的下合,当凌日可能发生时,预计在JD 2,455,315.2 +/- 1.9(以UT 17 h 2010年4月28日为中心)。

英文摘要:

We present new radial-velocity measurements of HAT-P-13, a star with two previously known companions: a transiting giant planet "b" with an orbital period of 3 days, and a more massive object "c" on a 1.2 yr, highly eccentric orbit. For this system, dynamical considerations would lead to constraints on planet b's interior structure, if it could be shown that the orbits are coplanar and apsidally locked. By modeling the Rossiter-McLaughlin effect, we show that planet b's orbital angular momentum vector and the stellar spin vector are well-aligned on the sky (lambda = -0.9 +/- 8.5 deg), suggesting that the planetary orbits are also well-aligned. The refined orbital solution favors a slightly eccentric orbit for planet b (e = 0.0142_{-0.0044}^{+0.0052}), although it is not clear whether it is apsidally locked with c's orbit (Δω= 48_{-38}^{+25} deg). We find a long-term trend in the star's radial velocity and interpret it as evidence for an additional body "d", which may be another planet or a low-mass star. The next inferior conjunction of c, when a transit may happen, is expected on JD 2,455,315.2 +/- 1.9 (centered on UT 17h 2010 April 28).

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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